Angioplasty procedures have gained wide acceptance in recent years as an effective and efficient method for treating certain types of vascular disease. For example, angioplasty is widely used for treating clogged arteries in the heart. Angioplasty is also used for the treatment of a wide variety of vascular restrictions in various other parts of the vascular system.
Angioplasty is commonly performed utilizing a balloon dilatation catheter which dilates the clogged artery, thereby re-establishing acceptable blood flow through the artery. An angioplasty balloon catheter typically includes an elongate tubular shaft and an inflatable balloon disposed at the distal end of the shaft. In use, the balloon catheter is advanced through the vascular system until the balloon is disposed adjacent the restriction in the artery. The balloon catheter is typically advanced over a guidewire which facilitates navigation through the vascular system. Once the balloon is in the desired position, the balloon is inflated for approximately 30 seconds to two minutes after which the balloon is deflated and withdrawn if acceptable blood flow has been re-established.
An example of such a balloon dilatation catheter is disclosed in U.S. Pat. No. 5,921,958 to Ressemann et al. Ressemann et al. disclose a balloon dilatation catheter having a guidewire lumen disposed distal of the balloon. The guidewire extends adjacent the catheter shaft and balloon, and passes through the guidewire lumen. When the balloon is inflated, the guidewire is disposed between the exterior of the balloon and interior of the vessel wall. The balloon and the guidewire collectively occlude the vascular lumen when the balloon is inflated thereby preventing blood flow. By preventing the flow of blood across the treatment site, an ischemic reaction may occur if the flow of blood is occluded too long. It is desirable, therefore, to provide a path for the flow of blood across the inflated balloon. Although balloon catheter designs which incorporate a perfusion lumen are known, it is desirable to provide a perfusion path without increasing the design complexity of the balloon catheter.
In addition to balloon angioplasty, intravascular ionizing radiation therapy is being used increasingly to treat vascular disease. For example, the administration of ionizing radiation has been proposed as both a primary and a secondary therapy for treating vascular restrictions. Clinical studies have shown that ionizing radiation may be used to inhibit or prevent restenosis after percutaneous transluminal angioplasty.
A conventional procedure for the intravascular administration of ionizing radiation utilizes a centering catheter to maintain the radiation source wire radially centered in the vascular lumen. Such centering catheters commonly comprise balloon catheters such as the devices disclosed in European Patent Application No. 688 580 A1 to Verin et al. Verin et al disclose centering catheters utilizing a multi-lobed balloon. In FIG. 3 of Verin et al., a centering balloon catheter is illustrated incorporating a guidewire lumen distal of the balloon, similar to the arrangement disclosed by Ressemann et al. In use, the catheter of this embodiment may also result in the occlusion of blood flow across the treatment site when the balloon is inflated. Because treatment times for the administration of ionizing radiation are commonly longer than inflation times for balloon angioplasty, the likelihood of causing an ischemic reaction is greater with this particular procedure. Accordingly, it is desirable to provide a perfusion path across the treatment site while the balloon is inflated. It is particularly desirable to provide a perfusion path across the treatment site without increasing the design complexity of the centering catheter.